The Involvement of NMDA receptor in the intrinsic analgesia evoked by hyperventilation

[背景]过度换气可增加中枢神经系统兴奋性氨基酸浓度。但是，没有关于过度换气的这种影响的报道。我们研究了过度通气时大鼠背角NMDA受体在介导神经元反应中的作用。[方法]雄性Spargue-Dawley大鼠氟烷麻醉。气管切开术后，对动物进行机械通气。将导管插入静脉和动脉，进行椎板切除术，并横断脊髓。将动物固定在立体定位架上。手术后，维持轻度麻醉。记录细胞外单细胞动作电位并测量锋电位发放率。通过形态和距脊髓背侧的深度识别WDR细胞。研究了四组：1。将竞争性NMDA受体拮抗剂2-Amino-5-phosphonovaleric（AP_5）0.16 μmol作用于脊髓， ...更多信息 记录诱发放电频率。2.换气过度组。给予过度通气，60分钟后恢复正常通气。3.治疗前研究。将AP 5施加到脊髓上。记录对AP 5给药的反应。随后，通过增加呼吸频率和潮气量来研究呼吸过度通气的作用。记录了击发速率。4.治疗后研究。给予过度通气，50分钟后给予AP 5，并研究AP 5的时间过程。[结果]低剂量的AP 5对WDR细胞的单位活性无影响。过度通气抑制背角神经元活动。过度通气后给予低剂量AP 5可显著增强过度通气的抑制作用。[结论]过度通气可激活NMDA受体，从而减弱过度通气对神经元活动的抑制作用。少

[background] Hyperventilation may increase the excitatory amino acid concentration in the CNS. But, there was no report about such effects of hyperventilation. We have investigated the role of NMDA receptors in the rat dorsal horn in mediating neuronal responses when hyperventilation was administered. [method] Male Spargue-Dawley rats were anesthetized with halothane. Following tracheotomy, the animals were mechanically ventilated. Catheters were inserted into veins and arteries and laminectomy was made and the spinal cord was transected. Animals were fixed on a stereotaxic frame. Following surgery, a light level of anesthesia was maintained. Extra-cellular single-cell action potentials were recorded and spike firing rate were measured. The WDR cell was identified by the modality and by the depth from the cord dorsum. Four groups were studied : 1. The competitive NMDA receptor antagonist, 2-Amino-5-phosphonovaleric, AP5 0.16 μmol was applied onto the spinal cord, both the spontaneous a … More nd evoked firing rate were recorded. 2. Hyperventilation group. Hyperventilation was administered and 60 minutes later, returned to normal ventilation. 3. Pre-treatment study. AP5 was applied onto the spinal cord. The responses to AP5 administration were recorded. Subsequently, the effect of respiratory hyperventilation was studied by increasing the respiratory frequency and tidal volume. The firing rates were recorded. 4. Post-treatment study. Hyperventilation was administered, and fifty minutes later, AP5 was administered, and the time course of AP5 was studied. [Results] AP5 at low dose had no effect on the single-unit activity of WDR cell. Hyperventilation depressed dorsal horn neuronal activity. After hyperventilation, the administration of AP5 at low dose profoundly enhanced the depressing effect of hyperventilation. [Conclusion] Our results suggest that hyperventilation activates NMDA receptors, thereby attenuating the inhibitory effect of hyperventilation on the neuronal activity. Less